With the spread of PCs and digital home appliances, it is becoming a reality to interconnect these devices via a home IP (Internet Protocol) network and to share and enjoy digital content, such as video, audio, and pictures. For example, DLNA (Digital Living Network Alliance) defines technical specification and implementing guideline needed for sharing digital content among these digital devices so that it is possible to interconnect devices of different vendors with each other, and DLNA has become an industry standard of home IP networks.
FIG. 1 shows an example of a home network 100 proposed by DLNA. A DVR (Digital Video Recorder) 101 and a PC 102 with a built-in TV tuner, as digital video content recording apparatuses, are capable of receiving satellite and terrestrial analog broadcasting and digital broadcasting, and record and save broadcast programs on built-in hard disk recorders. In DLNA, a device that stores content and that provides the content to devices in a home network is called a digital media server (DMS). In FIG. 1, the DVR 101 and the PC 102 are DMSs.
A DMS is capable of performing streaming transmission of, for example, video content of a TV program recorded on a hard disk to a digital media player (DMP) connected via a home IP network. The digital media player (DMP) is a device that receives content from a DMS and plays the content.
In the example shown in FIG. 1, a DMP is implemented on a TV 103, and, for example, by using an infrared remote controller or the like of the TV 103, a user can operate the TV 103 to play video content stored on the PC 102 or the DVR 101 placed in a remote room. Note that a residential gateway (RG) 104, which is used as a network connecting device in a case where a device in a home is connected to an IP broadband network 120 as the Internet, is used as a bridge for IP connection of a device in a home in the example of use of DLNA.
Meanwhile, a revolution is seen in broadcasting systems, and IPTV services, VOD (Video On Demand) services, and so forth that transmit video content via IP broadband networks, which has hitherto been broadcast using terrestrial waves or satellites, are coming to be commercialized. FIG. 2 shows a schematic diagram of IPTV and VOD services.
In a home, an STB (Set Top Box) 151 is installed so that it is possible to receive via the RG (Residential Gateway) 104 and via the IP broadband network 120 content based on services from various IPTV service providing servers 121 al to an and VOD service providing servers 122 b1 to bn. The STB (Set Top Box) 151 has a function of receiving video information, application executing functions needed for command transmission and reception, for MPEG decoding, and also for playing of received data, and so forth.
The residential gateway (RG) 104, in some cases, receives services (content) provided by a plurality of IPTV service providing servers 121 or VOD service providing servers 122 via the same agent, for example, an access line providing company such as a telephone company or a CableTV company, and in other cases, receives individual services separately. However, it is necessary that the STB (Set Top Box) 151 itself, used by the user, is configured as a system supporting an IPTV service of a connection destination.
As such IPTV services and VOD services become common in the future, similarly to the conventional sharing and viewing by DLNA devices of TV broadcast content as ordinary broadcast broadcasting, user's need arises for using video content provided from IPTV services on DLNA devices.
As proposed solutions for meeting such demand, a method in which a device having a large-capacity hard disk, such as a home server, downloads video content from an IPTV service and shares the video content in a home network, or a method in which a protocol, media format, and so forth of an IPTV service are converted at a residential gateway (RG) into a protocol and media format of a DLNA device and the IPTV service is provided to a home network connecting device, is conceivable. Note that a home-network embedded module that executes a format converting process is described in Patent Document 1.
However, in the former case, a time for downloading is needed for temporary storage at a home server, so that it is difficult to enjoy video when desired, which is possible with a video on demand service, and it is not suitable for live viewing. In the latter configuration in which processing is executed by a residential gateway (RG), it is necessary that the residential gateway (RG) executes protocol conversion and media format conversion, so that high-performance hardware is needed and software becomes complex, and the RG becomes expensive.
Generally, in many cases, an RG is supplied from an access line providing company (telephone company or the like) of a broadband network, and this becomes an obstacle in a case where IPTV services are provided on the open Internet, for example, IPTV services available for the user are limited to the vendor provided by the access line. Although it is possible to provide a new gateway device in a home IP network separately from the residential gateway (RG), in this case, depending on the network topology, content streaming data is transmitted in duplicates in the home network, so that such a situation occurs that a band in the home network is used in vain.
Note that an example of connection between a DLNA device in a home network and a content distribution service on the Internet is the Viiv (registered trademark) technology of the U.S. Intel Corporation. Viiv is considered as a platform of PC hardware and software, and is intended for stream viewing of content on a PC from the Internet by a Dual Core high-performance CPU. At the same time, Viiv has a DLNA function, and serves as a DLNA media server that performs streaming of content temporarily downloaded from the Internet to the PC to another DLNA device connected to the home network.    Patent Document 1: Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2005-531231